Well Donut...I'm NOT glad you asked!!!
The time honoured tradition of the Blumpkin first originated in france in 1704 when Marcelle Du'pont a well known ladies man and economist used to have the unfortunate habit of blowing both loads when getting a BJ from his mistress.
Sick of cleaning the bed sheets the mistress suggested that it would be easier if he simply sat on the poo repository whilst she did the deed. This worked out for the best and everyone was happy and she turned to Marcelle with her mouth still full of baby gravy and said "I love you pumpkin" but due to the full mouth it came out " I lub nu Blumpkin"..and so ...The Blumpkin was born.
To answer your question all you need do is simply say this "You know how women say a man cant multi task? ...follow me and I'll prove you wrong!" , you could also state the case of it being more efficient etc.
An alternative is to build up and train her for the Blumpkin, take it in easy stages..start by having a dump while she is in the room, get a handjob on the toilet, combine the two...then get a BJ whist sitting on the toilet...then add the poo.. Do it gradually..these things cant be rushed.
Anyway...hope it all works out for you, i'm off to lick out a girl while her grandma shits in my navel, whilst the mum is riding me getting it smeared all over her, with the dog licking my ring, while being banged by Norton . Wish us luck
Hope that helps,
Chalice